<!DOCTYPE html>
<html lang="en" style="font-size: 30px">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .outer{
            font-size: 20px;
        }
        .inner{
            /* font-size: 2em; */
            width: 10rem;
            height: 5rem;
            background: #caf;
        }
    </style>
</head>
<body>
    
    <div class="outer">
        <div class="inner">
            今天这个天气是真的有点凉啊!!
        </div>
    </div>
</body>
</html>